#85 Summary of Respiration

Credit: acsbiology.info

Respiration is a series of metabolic reactions that takes place in every living cell. The purpose of respiration is to release energy from glucose, so that the cell can make use of the energy.

• In aerobic respiration, the glucose is combined with O₂, forming CO₂ and H₂O.   

• In anaerobic respiration, the glucose is broken down without being combined with O2. In plants and fungi, this produces alcohol and CO₂. 

• In animals (including human) it produces lactic acid.

• Muscles respire aerobically when they are working so fast that they cannot be supplied with O₂ quickly enough. The lactic acid that is made is transported to the liver, and later is broken down by combining it with O₂. This extra O₂ is breathed in after the exercise has stopped, and it is known as the oxygen debt. 

•  All gas exchange surfaces need to be thin, have a large surface area, be kept moist, and have a good supply of O₂. In larger animals, a transport system is needed to carry away the CO₂ and bring O₂. 

• The air we breath in travels down the trachea and bronchi, through the bronchioles and into the alveoli. 

• Some of these tubes are lined with goblet cells which make mucus, and ciliated cells. The mucus traps dirt, bacteria and other particles and the cilia sweep the mucus up and away from the lungs. 

• Air is drawn into the lungs by the contraction of the external intercostal muscles and the muscles in the diaphragm. These muscle contractions increase the volume of the thorax, which decreases the pressure. Air flows down the pressure gradient and into the lungs. 

• Tobacco smoke contains many different substances that harm health. Nicotine is an addictive stimulant, and its intake increases the risk of developing heart diseases. Tar causes lungs and other cancers. CO₂ reduces the ability of red blood cells to transport O₂. Smoke particles irritate the lungs and can contribute to the development of emphysema.